August 2002 Table of Contents

Features Joints, Shrinkage, and Slab-Edge Support: An Open Challenge to ACI 302

A very important part of providing a durable concrete slab on grade is the proper treatment of control joints and construction joints. Support of the slab edges is one aspect often overlooked. Read more

Features Rising to the Challenge of Perfection

Past the 25,000-pound bronze doors of Our Lady of the Angels Cathedral in Los Angeles, the entrance corridor rises at a pitch of 95 feet per quarter mile. Cardinal Roger Mahony felt that through the effort needed to climb this "mountain" to the cathedral's nave, the penitent would shed the cares of the world and become ready to receive the word of God. Building this huge concrete structure required the construction team to undergo a similar change of mind. Read more

Features Intense Geometry

Shaped as if by the forces of wind and water, a curvilinear concrete edifice clad in limestone is rising in a place of honor on the National Mall in Washington, D.C. Scheduled to open in 2004, the Smithsonian Institution's National Museum of the American Indian (NMAI) will pay tribute to and preserve the culture and traditions of Native peoples of the Western Hemisphere. Read more

Features Tilt-Up Pioneer

Tornado-level winds passed through northwest Ohio in the summer of 1998, causing heavy damage to buildings and property throughout the region. Especially hard-hit was the Mess Hall at Camp Perry Military Reservation near Port Clinton. Camp Perry was established in 1906 to support the training requirements of the Ohio National Guard. Read more

Features Who Lost the Slump?

Lightweight concrete has its own set of potential placing problems, as every contractor knows. These problems were compounded 7 years ago when Albanelli poured suspended concrete slabs on steel decking for a high-profile shopping mall in suburban Detroit. Read more

Features Polishing Concrete with Diamonds

Imagine a concrete floor as shiny as glass—this is a look that diamond polishing can achieve. Two years ago very few people in the United States had even heard of polished concrete other than terrazzo floors. Terrazzo floors use carborundum stones to grind and polish floors to a 120- to 150-grit finish (grit refers to the micron particle size of the diamonds or other grinding abrasive material). Diamond-polishing technology now makes it possible to grind and polish much faster on concrete surfaces at up to 3000-grit finishes. Read more

Safety Matters Safety Report: It Won't Happen to Me

A concrete contractor was placing and finishing elevated concrete slabs on the metal deck of a municipal exhibition hall. Summertime temperatures and morning rush-hour traffic forced concrete deliveries to start at 4 a.m. Power buggies were used to transport the deck concrete. To provide a runway for the buggies and to protect the finished floor, crews laid out sheets of plywood. Read more

Concrete Basics When Is It Safe to Remove Wall Forms and to Backfill?

Stripping wall forms after 24 hours is common practice in our industry. Early formwork removal and backfilling keep construction schedules on track and provide easy access to the work—both important considerations—but safe? To avoid damage to concrete that may not have attained full strength or may be overloaded in the stripping or in subsequent construction operations, here are some guidelines. Read more

Problem Clinic Loose Exposed Aggregate

I live in Wanaka, which is in the south island of New Zealand, and recently laid 150 square meters of exposed aggregate paths and driveway. After laying and during the washing, we had problems getting rid of the water (all but one side of the house is bou Read more

Problem Clinic Rust in Exposed Aggregate

We use a 10-mm brown river aggregate in decorative exposed aggregate finishes. Read more

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